1. Field of the Invention
The present invention relates generally to automotive transmission clutches and more particularly to centrifugal pressure assist type clutches with adjustable centrifugal loading.
2. Description of the Prior Art
Severe loading created by rapid transfer of power from a vehicle's engine to drive train components is problematic in competitive environments. It has become common to use centrifugal type clutches in these high horsepower applications to control the rate of change of power transfer from an engine to a drive train by allowing slippage between the engine and the drive train. There have been several efforts in the prior art to provide a centrifugal clutch that has means for adjusting the amount of slippage between the engine and the drive train to allow adjustment of the point where the clutch stops slipping. Several previously issued United States patents disclosing centrifugal clutches providing means for adjusting the amount of slippage between the engine and the drive train are described here.
U.S. Pat. No. 3,580,372 issued to Schiefer discloses a centrifugal pressure assist type clutch. The clutch has a plurality of radially disposed release levers pivotally secured to the pressure plate. Each lever has a centrifugal weight to create a moment which is a function of the rotational speed of the lever that tends to pivot the lever about the pivotal connection to the clutch cover and forces the pressure plate against the driven disc. The adjustment of the dynamic loading is effected through movement of the position of the levers' pivot axes on the clutch cover relative to the lever pivot points on the pressure plate and therefore the movement of the lever at a given rotational speed.
U.S. Pat. No. 4,485,905 issued to Radbo et al. discloses a manually disengageable centrifugal clutch having an intermediate plate and a pressure plate that define a plurality of outwardly narrowing spaces for radially movable centrifugal weights spring biased towards the pressure plate. The intermediate plate is suspended on disengagement arms and is movable thereby away from the pressure plate. In one position at a certain distance from the pressure plate, the spaces for the centrifugal weights are widened so much that the weights cannot exert any pressure on the pressure plate. The clutch is thereby disengaged regardless of rotational speed with the disengaging force depending upon the spring force on the intermediate plate.
U.S. Pat. No. 4,989,711 issued to Schultz et al. discloses a controller for a centrifugal clutch with circumferentially spaced actuating weights having radially inwardly projecting actuating arms that pivot rearwardly as the rate of rotation of the clutch accelerates and the weights move to increase actuating pressure in and through the clutch. Supplemental weight means such as nut and bolt assemblies to increase the weight of the levers are disclosed.
U.S. Pat. No. 6,536,574 issued to Fehring discloses a centrifugal clutch with two weighted members that are pivotally mounted to the drive hub. Two spring members are operative between the drive hub and the weighted member to apply a restoring force to the weighted members. Under the influence of centrifugal force generated by the rotation of the drive hub, the weighted members pivots against the resistance of the spring member so as to engage the drive plates and thereby urge the drive plates into engagement with the clutch disc such that the driven member rotates with the drive plates.
U.S. Patent Application Publication No. US2003/0183477 issued to Chevalier discloses a centrifugal clutch for coupling a drive shaft to a driven member at rotary speed above a predetermined threshold having a centrifugal slider with a weight at one end. The slider slides on a frame from an extended radial position to a retracted radial position.
While these previously disclosed centrifugal clutches provide different ways of adjusting the movement of the lever arms operating against the throwout bearing, there remains a need for a throwout bearing lever having dynamic weight movement during operation of the clutch that improves the effectiveness of the centrifugal clutch. To answer this need, the claimed invention provides a throwout bearing lever having a dynamic adjustable weight assembly.
As will be described in greater detail hereinafter, the claimed invention differs from the previously proposed inventions and employs a number of novel features that render it highly advantageous over the aforementioned prior art.